NEW DELHI: On a day when the Narendra Modi government is celebrating the first anniversary of the implementation of the Goods and Services Tax, the Congress has hit out at the Centre calling the tax regime 'deeply flawed'.

"Beginning with the GST Constitution Amendment Bill, every step taken by the BJP govt with regard to GST was deeply flawed. The GST bills ignored the advice of the Chief Economic Adviser on many aspects of GST, notably on the rates," former finance minister and Congress leader P Chidambaram said.

He also attacked the Centre for the manner in which big economic decisions like GST and demonetisation were implemented. "The government did bad things in a big way - demonetisation. Or big things in a bad way - GST. The design, structure, infrastructure backbone, rates and implementation of GST were so flawed that GST has become a bad word among businesspersons, traders, exporters and common citizens," Chidambaram said.

However, Union Minister Piyush Goyal mocked the Congress for criticising the GST. "There was no disruption and the economic growth was not affected due to implementation of GST. I would like to tell P Chidambaram that 'Angoor khatte hain'," he said.

During the celebrations to mark one year of the implementation of GST, Goyal had said: "Goods and Service Tax has long term benefits for the economy. I would like to thank all political parties and leaders for their cooperation on GST. It has brought transparency."

Minister of State PMO, Jitendra Singh, also said that the implementation of GST had brought a behavioural change in common man. "This historic decision by Modi government had been pending for decades. Notwithstanding with what opposition says we go by evidence. Figures speak for themselves. It has produced a behavioural change in common man, to be a tax payer instead of a tax evader," Singh said.

Earlier in the day, PM Modi had congratulated the people of the country on 'GST day' and claimed that it has brought growth, simplicity and transparency. "It is: Boosting formalisation. Enhancing productivity. Furthering ‘Ease of Doing Business.’ Benefitting small and medium enterprises. #GSTForNewIndia," he tweeted.